JPH03200100A - X-ray microscope - Google Patents

Abstract

PURPOSE:To improve sensitivity and resolving power and to expand an application range by uniformly electrostatically charging the photoconductive layer of an electrophotographic sensitive body, placing a sample between the photosensitive body and an X-ray source and irradiating the sample with an X-ray. CONSTITUTION:The X-ray transmission image of the sample P is recorded as an electrostatic latent image on the photoconductive layer 9 of the electrophotographic sensitive body 8 disposed to face a microfocus X-ray tube 3 when the photoconductive layer 9 is uniformly electrostatically charged and the sample P is placed between the photosensitive body and the X-ray tube 3 and is irradiated with the X-ray. The surface of the photoconductive layer 9 is scanned by the electron beam radiated from a lens barrel 4 provided on the other surface side of the photosensitive body 8 during or after photographing. The secondary electrons of the quantity meeting the latent image potential are released from the spot irradiated with the electron beam at this time. The quantity of the secondary electrons is detected by a multichannel type video amplifier tube (MCP) 5 provided near the photoconductive layer 9 and the latent image potential is indirectly measured from the quantity of the secondary electrons. The output of the MCP 5 is converted via a control section 6 to a video signal which is visualized in real time by a CRT 16.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application J This invention relates to an X-ray microscope, and particularly to an X-ray microscope with improved sensitivity and resolution.

[Prior Art] Conventional X-ray microscopes are classified into contact types, imaging types, and scanning types. A synchrotron or a microfocus X-ray tube is used as a radiation source, and a silver salt film or an X-ray-sensitive polymer material is used as a photosensitive material for the contact type or imaging type.

In the contact type, a sample is brought into close contact with a photosensitive material and X-rays are irradiated to form a contact image. After development, the close contact image is observed under magnification using an electron microscope or the like. Also, imaging type XI!
A microscope places a sample between an X-ray source focused in a minute area and a photosensitive material or photocathode, and obtains an enlarged image of the sample. Then, photoelectric conversion is performed on the photocathode, or the photosensitive material is developed and observed under magnification using an electron microscope.

A scanning xi microscope directly scans a sample with a focused X-ray beam, and an X-ray detector installed on the back side of the sample detects the transmitted
There are known devices that detect lines and electronically provide an enlarged image.

[Problem to be solved by the invention] The resolution of the conventional X-ray microscope described above is 50 to 100°.
00 people, and the close-contact type has the highest resolution. However, the close-contact type requires a long time for exposure during photographing and also requires development processing, so it has disadvantages in that images cannot be observed in real time and elemental distribution images cannot be imaged. On the other hand, the imaging type has difficulty in digitizing images and imaging element distribution images, and its resolution remains at the same level as an optical microscope. However, it is impossible to observe biological samples in real time due to the sensitivity of the X-ray photoreceptor used in contact type or imaging type, and the structure of placing the sample in a scanning type vacuum chamber. , and along with the resolution problem mentioned above,
There are limits to the scope of application of line microscopes.

Therefore, the high-performance xfI! has improved sensitivity and resolution and expanded the range of applications! A technical problem arises that must be solved in order to provide a microscope, and the present invention aims to solve this problem.

[Means for Solving the Problems] This invention has been proposed to solve the above problems, and includes an electrophotographic photoreceptor that takes an X-ray transmission image of a sample and is arranged facing an X-ray source. A scanning electron beam radiator is provided opposite to the other surface of the electrophotographic photoreceptor, and a secondary electron detector is provided to detect secondary electrons emitted from the photoconductive layer of the electrophotographic photoreceptor. An object of the present invention is to provide an X-ray microscope characterized in that it is provided with a control section for converting the output of the secondary electron detector into an image.

[Function] In the present invention, an electrophotographic photoreceptor is disposed facing an X-ray source. A photoconductive layer formed of a photoconductive semiconductor film of the electrophotographic photoreceptor is uniformly electrostatically charged, a sample is placed between the XIa source, and X-rays are irradiated. The X-ray transmission image of the sample is recorded as an electrostatic latent image. Then, during or after photographing, the surface of the photoconductive layer is scanned by an electron beam emitted from a lens barrel disposed on the other side of the electrophotographic photoreceptor. At this time, secondary electrons are emitted from the electron beam irradiation spot in an amount commensurate with the latent image potential of the irradiation spot. The secondary electrons (1) are detected by a secondary electron detector provided near the photoconductive layer, and the latent image potential is indirectly measured from the amount of secondary electrons. Then, the output of the secondary electron detector is converted into a video signal via a control section and imaged in real time on a CRT.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the accompanying drawings. For convenience of explanation, conventionally known technical matters will also be explained at the same time.

In FIG. 1, (1) is an xIs microscope. The X-ray microscope (1) includes an electron beam probe scanner (2) and an
It is arranged with its optical axis facing the microfocus X-ray tube (3) that is the radiation source. The electron beam probe scanner (2) includes a lens barrel (4) and a multi-channel image intensifier tube (hereinafter referred to as MCP) used as a secondary electron detector.

) (5) and a control section (6) that controls the lens barrel (4) and performs image signal processing. The lens barrel (4
) The bottom end of the vacuum chamber (7) of the electrophotographic photoreceptor (
8) is removably attached. A photoconductive layer (9) is formed on the - side of the electrophotographic photoreceptor (8) by a photoconductive semiconductor film such as amorphous selenium, and the photoconductive layer (9) is directed into the vacuum chamber (7). There is. The lens barrel (4) has an electron gun (10), a focusing lens (11), a scanning coil (■), a zoomable electron lens, and a diaphragm (→) arranged from the top in the figure, and has the same configuration as a strobe scanning electron microscope. The imaging plane of the electrophotographic photoreceptor (8) is scanned with a strobe pulsed electron beam.The spatial resolution of the imaging plane of the lens barrel (4) is approximately 1μ, and the electron beam The beam probe scanner (2) alone can perform zooming observation at a magnification of about 300 times.In addition, an MCP (
5) is provided to read out an electrostatic latent image, which will be described later.

The output of the MCP (5) is inputted to the control computer (1) via the A/D converter (→) of the control unit (6). The control computer (0) digitally processes the input signal and outputs the video circuit ( At the same time, the scanning coil (■
The electron beam of the lens barrel (4) and the scanning of cRT (+*) are synchronized.

On the other hand, the microfocus X-ray tube (3) located at the bottom of the figure is housed in a vacuum chamber (In) and focuses the electron beam emitted from the electron gun (Seagull) with a focusing lens (A). , collide with the target (21) to produce a micro-focused X
A line is emitted onto the electrophotographic photoreceptor (8) above.

Further, the scanning coil (c) changes the position of the electron beam impinging on the target laser l-(21).

Next, the operation of the X-ray microscope (1) will be explained. First of all,
The photoconductive layer (9) of the electrophotographic photoreceptor (8) is uniformly electrostatically charged by corona discharge from a scorotron (not shown) or by an electron beam from an electron beam probe scanner (2). At this time, it is preferable to charge the battery negatively for reasons described later. Then, the sample (P) was attached to the electrophotographic photoreceptor (
8) and the radiation aperture (3a) of the microfocus X-ray tube (3).
), and by this position, it is possible to take images at a magnification of about 100 times from the same magnification taken in close contact with the electrophotographic photoreceptor (8). Therefore, together with the magnification of the electron beam probe scanner (2), a magnification of tens of thousands of times is obtained.

Then, the sample (P) is photographed by irradiating X-rays from the microfocus X-ray tube (3), and the photoconductive layer (9) is coated with the sample (P).
At the same time as forming the electrostatic latent image P), or after photographing, the photoconductive layer (9) is scanned by collimating the electron beam of the electron beam probe scanner (2) according to the zoom magnification. At this time, as shown in FIG. 2, secondary electrons (E) (E)...
・ is generated, accelerated by the grid (c), and MCP (
5). The amount of secondary electrons is determined by the photoconductive layer (9) and M
Due to the energy filter effect created by the space between the CP (5), the amount of electrons is perceived as being proportional to the potential of the electron beam irradiation point (S), and the indirectly measured potential of the electrostatic latent image is sent to the control unit (6). is converted into a video signal. The control section (6)
In combination with MCP (et al.), it has a potential resolution of about several IO mV, and a gradation resolution of 10 bits or more.

Here, as shown in FIGS. 3(A) and 3(B), the photoconductive layer (9
) is charged with a positive 1u charge, and if an electrostatic latent image is formed with positive charges, the electrostatic latent image is neutralized by the electron beam (B) of the electron beam probe scanner (2), and The generated secondary electrons (E) (E)... are neutralized by flowing into the vicinity of the electron beam irradiation point (S).

Therefore, it is difficult to read out the amount of secondary electrons compared to when an electrostatic latent image is formed with negative charges as shown in FIGS. 4(A) and 4(n). 9) should be charged with a negative charge. In addition, the surface of the photoconductive layer (9) is kept smooth in order to eliminate the adverse effects of secondary electron generation due to unevenness or inclination of the surface of the photoconductive layer (9).
It is necessary to maintain accurate levelness for B).

The electrostatic latent image is neutralized by irradiation with the electron beam (B), or charge-up progresses, the potential gradually decreases, and finally the electrostatic latent image disappears, and the electrostatic latent image on the photoconductive layer (9) The potential distribution becomes uniform. Therefore, the potential of a semiconductor such as amorphous selenium that is sensitive to X-rays decreases rapidly, and when continuously irradiated with an electron beam (B), the observation time is extremely short. Furthermore, the diffusion of minority carriers due to irradiation with the electron beam (It) has an adverse effect on the retention of the electrostatic latent image.

Therefore, in this embodiment, both the accelerating voltage and beam current of the lens barrel (4) are reduced to extend the time until charge-up, and the beam diameter is reduced by reducing the beam current to achieve an advanced space. Obtaining resolution.

In addition, the control unit (6) shown in Fig. 1 controls the irradiation timing of the electron beam (B) of the electron beam probe scanner (2), and irradiates it in the form of a strobe pulse only at the moment of sampling with an output of several KeV. Since charge-up is delayed and latent image data is collected before minority carriers are generated and diffused, the spatial resolution is reduced to about 10 to 100 times compared to continuous beam irradiation.

Furthermore, the above-mentioned strobe pulsed electron beam (B) is applied to the same point on the photoconductive layer (9) multiple times, and the amount of secondary electrons generated is added up in the buffer memory (15a) of the control computer 0→. An image with a good S/N ratio is obtained due to the integral effect. The above configuration has a resolution of 10 mm and a magnification of several tens of thousands of times, and enables the digitization of enlarged images of biological samples in real time, as well as the observation of elemental distribution images.

This invention can be modified in various ways without departing from the spirit of the invention, and it is natural that this invention extends to such modifications.

[Effects of the Invention] As described in detail in the above embodiment, the present invention reads image data from an electrostatic latent image photographed on an electrophotographic photoreceptor. Since the electrostatic latent image formed on the photoconductive layer of the electrophotographic photoreceptor has an electric charge as the smallest unit of screen formation, if the electrostatic latent image is electrically visualized, it becomes an X-ray photoreceptor with extremely high resolution. . However, it has been impossible to perform highly accurate scanning for imaging using conventional surface potential probes and the like. Therefore,
This invention uses an electron beam probe scanner formed by a lens barrel and a secondary electron detector, and is configured to indirectly measure the latent image potential, making it possible to use an X-ray microscope with extremely high resolution. Been formed. Since the potential of the electrostatic latent image is scanned and measured, input signals can be easily digitized, and high-quality images can be observed in real time.

In addition, the electrophotographic photoreceptor has extremely high sensitivity compared to conventional X-ray-sensitive polymer materials or silver salt films, so exposure time can be shortened, and it has a wide wavelength range of Vp to 1°Bvp. It can be used with a wide range of X-ray light sources, and it also makes it possible to observe biological samples in real time, making it extremely effective in improving the performance and functionality of X-ray microscopes and expanding their range of use.

[Brief explanation of drawings]

The figures show one embodiment of the present invention, Fig. 1 is an explanatory diagram of the configuration of an X-ray microscope, Fig. 2 is an explanatory diagram showing the detection operation of secondary electrons,
Figures 3 (A) and (B) are explanatory diagrams of the main parts showing the movement of secondary electrons when reading out an electrostatic latent image formed with positive charges, respectively, and Figures 4 (^) and (El) are respectively negative FIG. 3 is an explanatory diagram of main parts showing the movement of secondary electrons when reading out an electrostatic latent image formed by electric charge. (1)...X-ray microscope (2)...Electron beam probe scanner (3)
...Micro focus X-ray tube (4)...
... Lens tube (5) ... MCP (6) ...
...Control unit (8) ...Electrophotographic photoreceptor (9)
...Photoconductive layer (P) ...Sample
(E)...Secondary electron figure 2 (E)...Secondary electron figure 3

Claims (1)

[Claims] An electrophotographic photoreceptor for taking an X-ray transmission image of a sample is disposed facing an X-ray source, a scanning electron beam radiator is provided opposite to the other surface of the electrophotographic photoreceptor, and A secondary electron detector for detecting secondary electrons emitted from a photoconductive layer of a photographic photoreceptor is provided, and a control section is provided for converting the output of the secondary electron detector into an image. X-ray microscope.